Process for shaping textile articles using fluid thermoforming techniques

ABSTRACT

Articles are manufactured from textile material composed of filaments prepared from blended fiber-forming polymers having different chemical properties, at least one of the fiber-forming polymers being dispersed as fibrils in a lower melting point polymeric matrix. The article is produced by heating the material to a temperature above the melting point of the matrix-forming polymer but below the melting point of the dispersed fibrils to shrink said article thereby decreasing the porosity thereof and afterwards forming the heated material into a three-dimensional shape using vacuum or other fluid pressure.

Elited States atent Winchklhofer et a1.

[ June 27, 1972 PROCESS FOR SHAPING TEXTILE ARTICLES USING FLUID THERMOFORMKNG TECHNIQUES Inventors: Robert Charles Winchklhofer; Gene Clyde Weedon, both of Richmond, Va.; George Howard Collingwood, West Warwick, R.l.

Allied Chemical Corporation, Broadway, N.Y.

Filed: Oct. 30, 1970 Appl. No.: 85,692

Related U.S. Application Data Continuation-impart of Ser. No. 761,447, Sept. 23, 1968, abandoned.

Assignee:

U.S. Cl ..264/89,161/150, 161/170, 161/176, 264/92, 264/94, 264/230, 264/342 R Int. Cl ..B29c 17/04, B29c 23/00, D02g 3/04 Field of Search ..264/89, 90, 92, 93, 94, 230, 264/235, 342 R, 346; 161/150, 170, 176; 18/19 F References Cited UNITED STATES PATENTS 8/1944 Reed ..'.264'/; 3 0

11/1965 Such et a]. ..264/230 X 6/1967 Such ..264/342 R X FOREIGN PATENTS OR APPLICATIONS 899,646 6/1962 GreatBritain ..264/92 988,370 4/1965 GreatBritain ..264/92 Primary ExaminerRobert F. White Assistant Examiner-J. H. Silbaugh Attorney-Roy H. Massengill [5 7] ABSTRACT Articles are manufactured from textile material composed of filaments prepared from blended fiber-forming polymers having different chemical properties, at least one of the fiberforming polymers being dispersed as fibrils in a lower melting point polymeric matrix. The article is produced by heating the material to a temperature above the melting point of the matrix-forming polymer but below the melting point of the dispersed fibrils to shrink said article thereby decreasing the porosity thereof and afterwards forming the heated material into a three-dimensional shape using vacuum or other fluid pressure.

6 Claims, 11 Drawing Figures PATENTEDJUNZ? 1912 SHEET 1 BF 2 ri lilliilvt [NV ENT OR RoberfCMhc/r/hofer Gene 0 Wedan George H. Coll/ngwooa PATENTEDJuu27 192 3,673,295

sum 2 or 2 mvsmon Robert C W/hck/hofer Gene (2 Weedon George H. Co/l/ngwood Q flow PROCESS FOR SHAPING TEXTILE ARTICLES USING FLUID THERMOFORMING TECHNIQUES This invention is a continuation-in-part of application Ser. No. 761,447 filed Sept. 23, 1968 and now abandoned.

BACKGROUND OF THE INVENTION U. S. Pat. No. 3,369,057 which patent is hereby incorporated by reference as if fully set out herein) were originally prepared for employment in high strength yarns useful in yarn or cord form as reinforcing strands in elastometric tires and the like.

2. Description of the Prior Art Heretofore fluid thermoforming such as the heating of a non-air permeable vinyl film and vacuum forming it to a desired shape has been widely practiced in industry. However, such has not been practical in connection with open mesh textile articles because the porosity of the articles permitted the ready passage of the pressure-applying fluid and also because the plastic properties of the material at elevated temperatures was not conducive to satisfactorily utilizing them for such a process unless a non-air permeable sheet was employed in combination with the article as disclosed in British Pat. No. 899,646. lf heated, these fabrics have a tendency to sag thereby increasing the openness or porosity of said fabric. Further heating causes the polymer constituent to flow before heat setting is achieved and thereby destroys the textile appearance of the fabric.

It is well known that the physical characteristics of one polymer or a mixture of polymers can be varied greatly by changing the relative ingredient proportions or by mixing with another polymeric or additive material. Usually these are blend systems of polymers and/or copolymers wherein the various materials are mixed together to form a homogeneous mass which is then conventionally molded, calendered, etc., as described, for example, in Renfroe U.S. Pat. No. 3,336,173 wherein polyamide is blended with a polyolefin to improve the high frequency welding ability of the latter; Yasui et al. US. Pat. No. 3,322,854 disclosing homogeneous mixtures of polymers and/or copolycondensated polymers to improve polyester moldability, resistance to wrinkle and dyeability; and Fukushima U.S. Pat. No. 3,359,344 disclosing improved polyethylene, polypropylene or polystyrene calendered films made by incorporating chopped strands of a blended fiber comprised of polyolefin and a high molecular weight material.

SUMMARY OF THE INVENTION in accordance with the present invention unique new articles of textile materials having widespread useful value for clothing, automotive products, seating and many other applications is readily and economically carried out using highly developed thermoforming practices modified to accommodate the special characteristics of the unique poly-constituent materials used in the invention. These multi-constituent materials have a matrix containing a dispersion of discontinuous microfibers of fibrils with a substantially higher melting point than the polymer matrix in which they are present. When heated to a temperature near or above melt temperature of the lower melting polymer but below the melt temperature of the higher melting polymer, these materials shrank a substantial amount.

Although the various polymers are mixed together in this invention, they are not entirely intermiscible due to their physical properties and/or the mixing technique employed to assure a dispersion of microfibers. Microsized globules or fibrils are usually initially produced in the matrix, which when spun into filaments and drawn, produce the desired microfibrillar dispersion in the lower melting matrix material.

In accordance with this invention, it has been discovered that a textile fabric composed of filaments of the type described in U.S. Pat. No. 3,369,057 may be heat-treated and fluid-formed to a desired shape and yet the fabric will largely retain its original textile appearance. This is accomplished by heating the fabric to a temperature between the melting point of the polymers forming said filaments thereby shrinking and heat setting the filaments in situ in said fabric without significant flow, cross-sectional flattening, disfiguration, or sagging and at the same time a reduction in porosity of the fabric. As the filaments shrink, their diameter is increased to reduce the interstices of a fabric construction comprised thereof. Thus an important feature of this invention is that the fabric is heated to a heat-setting condition and maintained thereat throughout the fluid thermoforming phases of article production whereby permanent shaping is imparted to said articles when cooled. With the above as a basis, it was further discovered that various other polymer blend systems having at least two polymers of varying melt temperatures, one polymer being dispersed as discontinuous fibrils in a matrix of the other, can be employed to produce fluid thennoformed articles of three-dimensional shape, and although nylon-polyester blends of the type men tioned in the Twilley patent provide the best results, such other blend systems as will be described are intended to be embraced by, and included in, this invention. The principal objects of this invention are, therefore, to provide novel fluid thermoformed textile articles and methods of producing the same, without limitation to specific shapes or forms.

As used herein these terms are intended to have the following meaning:

Multi-constituent or matrix filaments filaments made by inclusion of at least one polymeric material in a matrix of another as discontinuous fibrils, the two materials having substantially different melt temperatures such that fibrous constructions composed thereof can be heat-set and plastically formed by application of heat below the melt temperature of one and equal to or above that of the other, the entire filament composition or any component thereof optionally including any secondary material compatible with the heat-set property of the fabric as a whole such as antioxidants and other stabilizing agents, reinforcing particles, fillers, adhesion promoting agents, fluorescent materials, dispersing agents, and others useful in polymerization, extruding, spinning, fabric forming and shaping, heat-setting and product finishing techniques. lf desired, inorganic materials such as metal whiskers, fiber glass fibrils, asbestos particles and the like may be incorporated for conductive and/or reinforcement purposes.

Textile material any woven, knitted or non-woven fibrous structure.

Fluid therrnofonning includes heating the textile material to a temperature whereby the lower melting matrix is at or above the temperature of fusion so that the fibers will begin or completely fuse together and shrink a sufficient amount to decrease the porosity of the textile material. The temperature should be maintained below the fusion point of the discontinuous fibrils to avoid unnecessary degradation of the textile material. While so heated, the heat-settable and heat-shrunk textile material has a differential pressure applied to it by means of a fluid in order to form it to a desired shape. The fluid can broadly include liquids as well as gasses and the pressure may either be direct pressure of the fluid itself or negative pressure by drawing a vacuum onto the textile material. The forming can be assisted by a combination of vacuum and pressure, by the use of slip rings around a die, the use of a plug as assistance, etc. Preferably, the article is formed by the use of ambient air pressure through pulling a vacuum on one side of the textile material after it has been partially fused. This can be accompanied by a plug assist if the shape of the textile material and conditions under which it is being formed indicate its use.

IAIAA'I Alan In general the invention is applicable to textile material prepared from heat shrinkable and heat-settable multi-constituent filaments or yarn of any combination of polymeric materials capable of creating a matrix and having a relatively higher melting dispersion of discontinuous fibrils; however, it is clear that a polyester-polyamide combination produces outstanding articles over the other materials. These compositions may contain 50-90 parts by weight nylon and 50-10 parts by weight polyester dispersion. Other materials useful in multiconstituent fibers are polyolefins, polysulfones, polyphenyl oxides, polycarbonates, and other polyarnides and polyesters. In any combination of any of the foregoing, the higher melting material is dispersed in the form of fibrils in a matrix of the other. In all of the blends mentioned hereinafter, heat-shrinkage, heat-setting and improved shape stability were achieved. Examples of the most useful polyolefin materials are polyethylene, polypropylene, poly-l-butene, polyisobutylene and polystyrene. In addition to the preferred nylon 6 (polycaproamide), other suitable polyamides are nylon 6-10 (hexamethylene-diamine-sebacic acid), nylon 6-6 (hexamethylene-diamine-adipic acid), methanoland ethanolsoluble polyamide copolymers and other substituted polyamides such as the alkoxy-substituted polyamides. The preferred polyester is polyethylene terephthalate; others are polyesters of high T useful in the practice of the present invention, including those polymers in which one of the recurring units in the polyester chain is the diacyl aromatic radical from terephthalic acid, isophthalic acid, S-t-butylisophthalate, a naphthalene dicarboxylic acid such as naphthalene 2,6 and 2,7 acids, a diphenyldicarboxylic acid, a diphenyl ether dicarboxylic acid, a diphenyl alkylene dicarboxylic acid, a diphenyl sulphone dicarboxylic acid, an azo dibenzoid acid, a pyridine dicarboxylic acid, a quinoline dicarboxylic acid, and analogous aromatic species including the sulfonic acid analogues; diacyl radicals containing cyclopentane or cyclohexane rings between the acyl groups; and such radicals substituted in the ring, i.e., by alkyl or halo substituents.

Many objects and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view in schematic form showing a drape-forming step where the textile material is being heated.

FIG. 2 is similar to FIG. 1 with the textile material being draped and vacuum formed to final shape.

FIG. 3 is similar to FIG. 1 except showing a slip ring and a different apparatus.

FIG. 4 is similar to FIG. 3 but shows the slip ring contacting the textile material and the beginning of the forming of the material into a three-dimensional shape.

FIG. 5 is similar to FIG. 4 with the material being formed into its final shape and the slip ring being further compressed.

FIG. 6 is similar to FIG. I but shows the utilization of a plug assist and a different type of apparatus.

FIG. 7 is similar to F IG. 6 but shows the heater removed and the plug in its descended position.

FIG. 8 is similar to FIG. 7 with a vacuum utilized to pull the fabric into its final shape.

FIG. 9 is similar to FIG. 1 showing the use of a different apparatus where pressure is used on one side and vacuum is used on the other side.

FIG. 10 is similar to FIG. 9 with the heater plate descended against the textile material which is locked against the forming cabinet.

FIG. 11 is similar to FIG. 10 with the textile material in its finally formed shape.

DESCRIPTION OF THE INVENTION As a first example of the practice of this invention, multiconstituent filament is produced in accordance with the formulation of Example 1 in U.S. Pat. No. 3,369,057, i.e., granular polyethylene terephthalate polymer was used, melting about 255 C. (DTA) and about 265 C. (optical), having density (when amorphous) of about 1.33 grams per cc. at 23 C. and about 1.38 grams per cc. in the form of drawn filament, having reduced viscosity of about 0.85 and having '1', about 65 C. The polyester in the form of drawn filament drawn to give ultimate elongation not above 20 percent will have tensile modulus (modulus of elasticity) ranging from about 70 to about grams per denier, depending on spinning conditions employed.

This polyester (30 parts) was mixed with 70 parts of granular polycaproamide having reduced viscosity about 1.04, T, about 35 C. and density about 1.114 grams per cc. at 23 C. Amine groups in this polycaproamide had been blocked by reaction with sebacic acid, bringing the amine group analyses thereof to 11 milliequivalents of NI-I groups per kilogram of polymer. This polycaproamide contained as heat stabilizer, 50 ppm copper as cupric acetate.

The mixture of polyamide and polyester granules was blended in a double cone blender for 1 hour. The granular blend was dried to a moisture content of no more than 0.01 percent; then melted at 285 C. in a 3-7-inch diameter screw extruder operated at a rotational speed of about 39 rpm to produce a pressure of 3,000 psig at the outlet. A dry nitrogen atmosphere was used to protect the blend against absorbing moisture. Residence time in the extruder was 8 minutes.

The molten mixture thereby obtained had melt viscosity of about 2,000 poises at 285 C. The polyester was uniformly distributed throughout .and had average particle diameter of about 2 microns, as observed by cooling and solidifying a sample of the melt, leaching out the polyamide component with formic acid and examining the residual polyester material.

The multi-constituent blend thus produced was extruded through a spinneret plate and the resulting solidified fibers were drawn and wound at 1,000-2,000 feet per minute under tensions of about 0.01 gram per denier. The filaments were then drawn 4-6 times their length in order to impart orientation and maximum strength thereto. The fibers were then formed into a yarn denier of grams per 9,000 meters. This 150 denier yarn was made up of 32 individual fibers. The yarn was then woven into a plain-weave fabric and fused on a tenter frame traveling at the rate of 7 yards per minute with a traction of 4 percent and an overfeed of +10 percent at between 215 C. and 230 C. and preferably 226 C. The air permeability or porosity was reduced from approximately 17 cubic feet per minute per square foot before heat treatment to 5 cubic feet per minute per square foot as measured by a standard test. A 6-inch by 6-inch sample of this fabric was clamped in a standard vacuum forming machine over a circular female mold one inch deep and 2-% inches in diameter. The retractable heaters were maintained at a temperature of 700 F. in a vicinity close to the heating elements so that the fabric is heated to below 226 C. and preferably to a temperature of between 218 and 226 C. prior to the application of the vacuum for approximately 20 seconds. The vacuum was then applied and the material readily assumed the 1-inch deep by 2-% inch in diameter three-dimensional shape and demonstrated the ease with which a textile article can be made by vacuum forming utilizing the principles of the present invention without the use of an impervious sheet material.

The machinery used in the above example is quite well known in the field of vacuum forming. Other types of machinery as illustrated in the drawings FIGS. 1 through 11 will now be described. In FIGS. 1 and 2 there is shown a drape-forming method and apparatus. The textile sheet is clamped by clamps 20 and heated by heater 21 to the desired temperature. The sheet is then drawn over the mold 22 or else the mold is forced up into the sheet. When the mold has been forced into the sheet and a seal 23 created, vacuum is then applied through opening 24 into cavity 25 and through second vacuum opening 26 so that atmospheric pressure is used in causing the heated textile material to stretch slightly and assume the shape of the mold. During the stretching operation there may be some tendency to reduce the normal decrease in porosity created by the spaced between the individual yarns opening up. However, in a properly selected textile material treated with proper fusion temperatures and sufficient capacity in the vacuum apparatus, such openings are insufficient to prevent the practice of the process.

In FIGS. 3, 4 and 5 there is shown a slip ring forming process. The heated textile material is placed across the female die 27. As the press closes pressure pads 28 clamp the textile material tightly to allow it to slip under control tension as the mold 27 is pushed into the material. During the descent, air beneath the sheet is either vented or else a vacuum is drawn through opening 30. As the mold finally closes the pressure pads exert maximum holding pressure against the textile material restraining it enough to avoid losing the final fonn shape. In the final view as seen in FIG. 5 vacuum can be applied through second opening 31 and if desired air pressure can be supplied through opening 30.

In FIGS. 6 through 8 are shown three sequences using vacuum forming plug assistance. After the textile material is heated by retractable heater 32 and sealed across the mold cavity 33, a plug 34 shaped roughly as the mold cavity but smaller is plunged into the textile material and prestretches it when the plug platen 35 has reached its closed position as shown in FIG. 7. A vacuum is drawn on the mold cavity through opening 31 to complete the formation of the textile object as is shown in FIG. 8.

In FIGS. 9 through 11 there is shown a sequence of steps using a trapped textile layer with contact heat and pressure forming. The textile material is inserted between the mold cavity 37 and a hot mold plate 38. The plate is flat and porous and allows air to be blown through its face. The mold cavity seals the material against the hot plate. Air pressure applied from the female mold cavity 37 through opening 39 beneath the sheet blows the sheet totally against the contact hot plate for the best thermal conductivity for rapid heating of the material. A vacuum can also be drawn on the hot mold plate. After a predetermined heating the textile material is ready for forming and air pressure is applied to the hot plate to form the sheet into the female mold as shown in FIG. 11. Venting can be used on the opposite side of the material or a vacuum can be applied through opening 39.

As a second example in practicing the process and making articles as a result thereof, the first example above is repeated except that the step by which the material was heat-set or fused in a tenter frame was omitted. Instead the material was directly used in apparatus similar to FIGS. 3, 4 and 5, utilizing a heating temperature of 2l8-226 C. The fabric exhibited a high shrinkage and was permitted to pull out of the clamping frame under controlled pressure of the clamping pads. This pressure was adjusted to apply a restraining force just sufficient to prevent wrinkling of the side walls of l-inch deep by 2-%-inch diameter cup which was formed. The free unrestrained shrinkage of this fabric, which was soft and flexible, was determined beforehand in an air circulating oven with the sample lying flat and unrestricted. At a temperature of 180 C. for 5 minutes it shrank 16 percent in the machine or warp direction and 14 percent in the transverse or fill direction. When heated to 200 C. for 5 minutes it shrank 21 percent in the machine or warp direction and 19 percent in the transverse or fill direction. In all of the above instances the shrinkage of the fabric was sufficient to close the interstices of the fabric to the extent that a differential air pressure could be imposed against said fabrics.

As a third example, the poly-constituent fiber of the first example was made into a yarn of 840 denier using I36 individual filaments. This yarn was then used for the warp and an 840 denier polyester yarn was used for the fill in producing a satin weave. A 6- by 6-inch sample of the fabric was placed in a plug-assisted vacuum forming apparatus similar to that of FIGS. 6 through 8. It was first heated to between 226 and 232 C. prior to forming into a cup l-inch deep by 2-%-inch in diameter. While the cup formed was satisfactory, the weave had a tendency to open up and be more porous during the forming operation, for it was necessary to use a plug for assistance and likewise a greater capacity to the vacuum pump was needed to continue to maintain sufiicient differential pressure to adequately form the material into the comers cavity.

As a fourth example, the third example was repeated with the only difference being that the weave was a plain weave rather than a satin weave. The results were identical to those of the third example.

As a fifth example of practicing the invention, the first example was repeated except the fibers of the textile material were not prefused in a tenter frame and the fibers used in making the textile material were only partially drawn. In the first example above the fibers had been substantially fully drawn in their manufacture, that is with a draw ratio of 4 to 6 or higher in order to confer molecular orientation along the filament axis to increase the strength of the filaments. While these highstrength filaments are usually desired, in some instances it has been found their tendency to shrink when heated to the fusion temperature of the matrix polymer creates more shrinkage than is desired to some uses. In this fifth example, the fibers were only drawn 2X. Their extruded length provided some molecular orientation and increase in strength but not nearly to the degree a further drawing would have provided. The fabric woven from this filament was similar to the first example and was heated in the first instance just prior to being vacuum formed in an apparatus similar to that of FIGS. 1 and 2. The 1 -inch deep by 2-%-inch diameter cup was readily formed in the apparatus with small clamping forces since the tendency to shrink had been reduced. It is to be noted that the fusion or heat stabilization in a tenter frame was omitted in this example.

As an example of a blend of two different materials in the same general class, a blend was prepared consisting of 30 percent polyethylene and 70 percent polypropylene by weight.

Both resins were commercially available grades. The blend was spun into a filament employing conventional spinning techniques. After spinning and drawing, the filament was used to produce a fabric which was heat-set in accordance with the principles outlined above except the temperature was kept below about C.

In addition, still other blends are satisfactory for purposes of this invention, including those disclosed in U. S. Pat. Nos. 3,378,055, 3,378,056 and 3,378,602; British Pat. No. 1,097,068; Belgian Pat. No. 702,803 and Dutch Pat. No. 66,06838. Usually, the melt temperatures of the blended polymers differ by about 10 C. or more.

For any given multi-constituent formulation, the temperature and time and fluid pressure will vary depending on the polymeric materials, article size, shape, desired rigidity, mode of heat application and other variables. In general, it is necessary to apply heat without excessive degradation of sufficient intensity and duration at least as high as the melting point of the matrix component until the fabric yarns have fused to each other and the porosity reduced whereby differential air pressure may be imposed yet still retain the yarn or fabric identity.

If the fabric yarns are spun from polyblend staple fibers, the

fibers forming said yarn will fuse together individually in addition to fusion at the cross points of said fabric. Fusion can be achieved without undesirable flow and no sag when initially heated and before forming.

In test results, the general observation is made that as the fabrics become increasingly fused at temperatures above the melting point of the higher melting component their strength, elongation and wrinkle resistance is reduced while their abrasion resistance, stiffness, dimensional stability, and gas and liquid permeability are increased. Fusing does not seem to affect the fabrics ability to be dyed, colorfastness to light and washing, or their wash stability. The invention is applicable to many fields such as apparel, home furnishings, transportation vehicles, sporting goods, and the like.

IAIAAR A...

The invention may be embodied in other specific forms Without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appendant claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

We claim:

I. A process for permanently shaping textile articles from heat-shrinkable and heat-settable matrix fibers having a higher melting component dispersed throughout said matrix which comprises:

a. positioning a layer of a porous textile material prepared from said matrix fibers adjacent to a three-dimensional form,

b. heating the layer of porous textile material at least to about the melting temperature of the matrix but below the melting temperature of the dispersed component to shrink the fibers and thereby reduce the porosity of said layer of material enough to enable shaping of the material by applied differential fluid pressure alone,

c. applying a differential fluid pressure against said layer of material while in a heat-setting condition to conform said fabric to the shape of said three-dimensional form without the use of a non-air permeable sheet, and

d. cooling said material to provide a permanently shaped three-dimensional textile article.

2. A process as described in claim 1 wherein the layer of textile material is cooled after the heating step so that a heatstabilized intermediate product of reduced porosity is achieved and then reheating said material to a temperature below the melting temperature of the dispersed component just prior to applying the differential fluid pressure.

3. A process as described in claim 1 wherein the matrix is composed of greater than 50 parts by weight polyamide and the dispersed component is composed of discontinuous fibrils of polyester.

4. A process as described in claim 3 wherein the polyamide is polycaproamide and the polyester is polyethylene terephthalate.

5. A process as described in claim 3 wherein the said material is heated to about 200 C. to about 250 C.

6. A process as described in claim 5 wherein the porosity of the starting material is reduced from an air permeability rate of about 15 cubic feet per minute per foot square to about 5 by said heat treating. 

2. A process as described in claim 1 wherein the layer of textile material is cooled after the heating step so that a heat-stabilized intermediate product of reduced porosity is achieved and then reheating said material to a temperature below the melting temperature of the dispersed component just prior to applying the differential fluid pressure.
 3. A process as described in claim 1 wherein the matrix is composed of greater than 50 parts by weight polyamide and the dispersed component is composed of discontinuous fibrils of polyester.
 4. A process as described in claim 3 wherein the polyamide is polycaproamide and the polyester is polyethylene terephthalate.
 5. A process as described in claim 3 wherein the said material is heated to about 200* C. to about 250* C.
 6. A process as described in claim 5 wherein the porosity of the starting material is reduced from an air permeability rate of about 15 cubic feet per minute per foot square to about 5 by said heat treating. 